Waxing, painting, sanding....these weren't really meant to teach Daniel-san how to block or even touch the basics of karate. That part was convenient moviemaking.

Mr. Miyagi realized Daniel was a whiny, weak brat who hadn't done an honest day's work in his life. How can you possibly learn REAL Okinawan karate if you're a skill-less punching bag who keeps picking fights with Kobra Kai senior students?

Miyagi thought "what a royal American dumbass....I better toughen him up or he's gonna get himself killed and then his mom will sue me, then it's sayonara for my sweet janitor gig".